Solid lubricant



p 3 A. R. BOBROWSKY 3,105,048

' I SOLID LUBRICANT I Filed Jan. 23, 1961 FIG. 2

INVENTOR. ALFRED R. BOBROWSKY ATTORNEYS United States Patent ice l 5,... 24, 1%.

3,105,048 SQLID LUBRICANT Alfred R. Bohrowsky, Florham Park, N.J., assignor to Engelhard Industries, Inc., Newark, NJ., a corporation of Delaware Filed Jan. 23, 1961, Ser. No. 83,994 3 Claims. (Cl. 25212) This invention relates to a solid lubricant, and. more particularly to a method for producing a solid lubricant capable of being formed into self-lubricating solid articles, and the self-lubricating article per se.

Lubrication of moving parts of machines is of course essential to diminish friction and prevent premature wearing out and damaging of the parts. However, at times it is difiicult to lubricate the moving parts by liquid lubricants because of inaccessibility of these parts.

In accordance with the present invention, a solid lubricant is provided which is capable of being formed into self-lubricating shapes, for instance self-lubricating thrust washers for use in machinery Where it is diflicult to lubricate by liquid lubricants. The solid lubricant of this invention is prepared by intimately admixing a lubricating grease, for instance cup grease, and graphite, and then compressing this admixture by application of high pressure, preferably from about SOD-15,000 pounds per square inch, more preferably from about 1000-5000 pounds per square inch. The product obtained is a solid, coherent non-tacky mass typically in sheet or slab form and of non-pasty consistency, exhibiting some flexibility, and lending itself to further processing such as the stamping or cutting of shapes therefrom. Further, the product solid lubricants have an entirely adequate strength for usual shop handling, although they might be restricted to applications Where the thrust pressure on them will not exceed the forming pressure. An additional use of the solid lubricants of this invention are as gas seals where rubbing against a shaft must not spoil the shaft.

The quantity of grease utilized may range from about 35-70 Weight percent, and the graphite from about 65-30 weight percent of the total weight. Preferred amounts of grease are from about 4860 weight percent, and of graphite from about 52-40 weight percent.

Lubricating greases are heterogeneous mixtures of mineral oil and usually soap, the soap serving to thicken the oil. The soap is usually a metfllic salt of a higher fatty acid and is made from animal or vegetable oils high in stearic, oleic and palmitic acids. Exemplary of the greases are lime base greases and soda soap greases. Lubricating greases were generally made heretofore by saponifying animal fats or rosin in mineral oil. Alumi num oleate or stearate are used as the thickeners in some grease lubricants. Other soaps utilizable as thickeners are soaps of barium or lithium, for instance barium or lithium stearate. Synthetic lubrication oils can also be used for combining with the soaps to form greases. Typical of such synthetic oils are the oils of low pour point, high viscosity index and low volatility prepared by esterfying octyl alcohols, for instance 2-ethylhexanol, with dibasic acids such as adipic and sebacic acids. The term lubricating grease is used herein in a broad sense to include lubricating compositions comprising either mineral oil or synthetic lubricating oil and a thickener, for instance soap. Use of cup grease was found to give excellent results in forming the solid lubricant. Cup grease is a lime base grease which can be formed by saponifying an animal fat with slaked lime, and spraying the resulting product with a light colored mineral oil.

The intimate admixing of the lubricating grease and graphite can be carried out with conventional and well known mixing means, for instance with a screw propellor mixer.

The pressures may be applied to the admixture of grease and graphite by means of dies, or if desired, by means of flat plates. The time of application of such pressures may range from about 1 second-about 1 week, preferably from about 1 minute5 minutes.

It was unexpected and surprising that the application of high pressure in accordance with the invention produced the solid non-tacky lubricant mass of this invention characterized by having excellent lubricating properties. The graphite employed in the method is preferably finely divided, and has typical particle size of about 0.1 micron up to 10 microns.

The solid, coherent product of the compressing, which is typically in sheet form, can be stamped, i.e. cut out by pressing with conventional stamping apparatus, to obtain the desired shape. Alternatively, articles of the desired shape can be formed from the solid product by cutting alone. The solid product of the compressing, which exhibits a non-tacky consistency and has some flexibility as previously mentioned, contains the graphite interspersed throughout the lubricating grease.

In FIG. 1 of the accompanying drawings, a self-lubri eating thrust washer 10 is shown. The washer has a plate-like body 11 having central opening 12 therein. This thrust washer was formed by compressing an intimate admixture of the lubricating grease and graphite as previously described to form a solid, non-tacky sheet, and then stamping this washer firom the sheet. FIG. 2 is a section taken on line 2-2 of FIG. 1. FIG. 3 shows a self-lubricating half-bearing 13 having a curved strip body 14 with concave inner surface 15 and convex outer surface 16. Bearing 13 is also formed from the intimate admixture of lubricating grease and graphite previously described. FIG. 4 is a section taken on line 44 of FIG. 3.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

l. A self-lubricating article comprising a shaped solid coherent mass of lubricating grease having graphite interspersed therein, said article being obtained by intimately mixing graphite and lubricating grease in the proportions of from about 35-70 weight percent of the grease and from about -30 Weight percent of the graphite, compressing the resulting mixture under pressure of about 5,00015,000 pounds per square inch for a period sufficient to form a solid coherent shapeable lubricant mass, and shaping the lubricant mass into the desired shaped article.

2. A method for producing a solid lubricant, which comprises intimately admixing finely divided graphite and lubricating grease in the proportion of from about 3570 weight percent of the grease and from about 65-30 Weight percent of the graphite, and compressing the admixture 7 References Cited in the file of this patent under pressure of about 500015,000 pounds per square inch for a period to form a solid lubricant. UNITED STATES PATENTS 3. A method of preparing a self-lubricating solid arti- 1 390 197 Dower Se t 6 1921 cle, which comprises intimately admixing finely divided 5 1589919 Adams 1926 graphite and lubricating grease in the proportions of from 2223272 R h "Ti" N 1940 about 35-70 Weight percent of the grease and from about 0e net 6 a 65-30 weight percent of the graphite, compressing the ad- OTHER REFERENCES mlxture under a pFessure of q about SOOOISOOO Manufacture and Application of Lubricating Grease, pounds per square mch for a period of from about 1-5 10 by Boner, Reinhold Publ Corp York, 1954, pages minutes to form a solid coherent shapeable lubricant 332 411 and 412.

mass, and shaping the solid lubricant into a self-lubricating article of the desired shape. 

1. A SELF-LUBRICATING ARTICLE COMPRISING A SHAPED SOLID COHERENT MASS OF LUBRICATING GREASE HAVING GRAPHITE INTERSPERSED THEREIN, SAID ARTICLE BEING OBTAINED BY INTIMATELY MIXING GRAPHITE AND LUBRICATING GREASE IN THE PROPORTIONS OF FROM ABOUT 35-70 WEIGHT PERCENT OF THE GREASE AND FROM ABOUT 65-30 WEIGHT PERCENT OF THE GRAPHITE, COMPRESSING THE RESULTING MIXTURE UNDER PRESSURE OF ABOUT 5,000-15,000 POUNDS PER SQUARE INCH FOR A PERIOD SUFFICIENT TO FORM A SOLID COHERENT SHAPEABLE LUBRICANT MASS, AND SHAPING THE LUBRICANT MASS INTO THE DESIRED SHAPED ARTICLE. 